Beleaguered U.N. peace envoy Kofi Annan will host an international conference to address Syria‘s rapidly escalating civil war, but the meeting in Geneva on Saturday appears to have only lukewarm backing from the U.S. — and then only after Washington put the kibosh on the attendance of Iran, whose participation had been deemed vital by Annan. Secretary of State Hillary Clinton indicated Wednesday that the U.S. would join representatives from Russia, China, Britain, France, Turkey, the EU and the Arab League in Geneva. The purpose of the meeting, per Annan, is to forge a consensus on the terms for a political solution among international players with stakes and influence in the Syrian conflict over terms for a political solution. The U.N. envoy believes that the best hope of pressing the combatants on the ground to observe his peace plan to which they signed up in April but have not implemented, is for the foreign powers on whose support they variously depend to agree on terms.

But even such key players as the U.S. and Russia can’t agree on a mechanism to resolve the conflict, and the exclusion of Iran and Saudi Arabia after the Obama Administration blocked Tehran’s participation suggests that Saturday’s meeting will simply restate the diplomatic stalemate.

“I have made it quite clear that I believe Iran should be part of the solution,” Annan said in Geneva last Friday. “If we continue the way we are going and competing with each other, it could lead to destructive competition and everyone will pay the price.”

The Obama Administration cited Iran’s role in backing up Syria’s bloody crackdown to declare Tehran’s involvement a “red line” for participating in the Geneva talks, and Annan presumably left out Saudi Arabia as a compensatory gesture to Russia which insists that those countries arming and funding Syria’s rebels share major responsibility for escalating the conflict. But it’s precisely because Iran and Saudi Arabia are playing out their preexisting regional and sectarian rivalries in the Syrian civil war that Annan wanted them at the table if there was to be any hope of achieving a solution without further bloodshed. Many in Washington, however, see the Syrian conflict through the same prism as Saudi Arabia does, seeking the ouster of Assad — Iran’s most important Arab ally — precisely in order to weaken Tehran.

Annan may be correct that such geopolitical competition is an obstacle to resolving the crisis, but that doesn’t mean his warning will be heeded: Not only are the Saudis and Iranians slugging it out via their Syrian proxies, but U.S.-Russian tensions are reinforcing the deadlock.

The Obama Administration was reportedly even planning to condition U.S. participation in the Geneva talks upon Russia endorsing the demand that President Bashar Assad step down — a position Moscow has vigorously rejected, insisting that it is not up to outside powers to dictate who rules Syria. Reuters has reported that Russia supports Annan’s proposal to form a national unity government in Syria, but Annan’s plan doesn’t explicitly exclude Assad, which means Russia could still insist he stay in power. Last week, Russian Foreign Minister Sergei Lavrov warned that Russia would not permit “a replication of the Libyan scenario in Syria,” dismissing as “unrealistic” the Western demand that Assad stand down. Still, U.S. officials insist that the Geneva meeting set clear guidelines for Assad stepping down as part of a political transition.

“If Kofi Annan can get the proposed participants to agree on such a plan for political transition then there will be a meeting,” a State Department official told reporters on Tuesday. “But that’s what we need to find out before we go to any meeting. There’s no point in going just for the sake of it.”

There’s no indication, as yet, however, that Moscow plans to oblige. Russia is continuing to supply weapons to the Assad regime under contract, stressing that these are weapons systems that allow Syria to defend its borders against “external aggression” — by which, of course, Russia would include any NATO intervention. Moscow was antagonized last week when Britain used the withdrawal of maritime insurance as a pretext to turn back a ship carrying Syrian attack helicopters that had been in Russia for repairs — the shipment is being dispatched once more under a Russian flag. Nor did Moscow condemn Syria for shooting down a Turkish warplane that the Syrians say had ventured into their airspace late last week.

But the NATO response to the downing of an aircraft of one of its member states was indicative of the limited options available to Western countries: an incident that would surely have been used as a pretext for a major escalation in the standoff had Western powers been planning military intervention drew, instead, a relatively timid response. Both the alliance, and Turkey itself, appear concerned to avoid escalating an already grim, sectarian conflict.

Indeed, the parties that will meet with Assad in Geneva have different ideas on resolving the crisis, but none appears to have decisive leverage to bring to bear in order to shape its preferred outcome. The U.S. insists that the conflict can’t be resolved while Assad remains in power; the Russians point out that Washington has no credible plan for dealing with the fallout that would follow the regime’s precipitous collapse. For much of the past year, officials in Washington have speculated that Russia might break with Assad, but the passage of time has made those claims look Pollyannaish.

Indeed, Russia’s willingness to push back against U.S. plans for tackling the Syrian crisis were evident in its effort to support Iran being invited to Annan’s conference. The U.S. nixed that idea, meaning that the conference that will be held in Geneva will be more limited in its scope and ambition. And nobody is expecting an outcome that makes much difference what even Assad himself now calls a “state of war” in Syria.